However, "early momentum" from the Apple Watch "triggered" Best Buy to expand and accelerate the rollout, Joly said during a conference call to discuss the company's second-quarter earnings.

Joly didn't say how many Apple Watches the chain has sold so far. Apple hasn't shared watch sales data either.

During Apple's third quarter earnings conference call, CEO Tim Cook said customers would have more ways to purchase the smartwatch because the company expects it to be a popular Christmas gift. A few days later, Best Buy said it would carry the wearable.

Best Buy is the only major retailer to stock the Apple Watch. The device can also be purchased from Apple's retail and online stores and from a few high-end clothing and department stores.

Joly also discussed plans to expand Best Buy's relationship with Apple.

The Apple shop-in-a-shop sections of 740 Best Buy stores are getting a makeover, with new fixtures and larger display tables to show Apple hardware, he said. So far, Best Buy has remodeled 350 of those departments and will revamp another 170 by the holiday shopping season.

Starting this quarter, Best Buy will begin selling Apple Care support plans while 50 stores will test offering Apple repair services. The CEO didn't mention what has to happen to make Best Buy a permanently authorized service provider and to expand the offering.